Paraffin hydrocarbon isomerization



Patented Jan. 13, 1948 2,434,338 PARAFFIN'HYDR0CARB0N IS0MERIZATION ErnestSolomom-Nutley, N. J2., assgnor to' The M".

W. Kellogg Company, Jersey YCity, N: J'., a corporation of Delaware Application January 29, 1942,.Seral. No.y 428,646

4 Claims. (Cl. Zink-683.5)`

The present invention relates Yto the conversion of light normal parain hydrocarbons into.v

branched chain hydrocarbons .in the presenceof a metallic halide catalyst, and one of .its objectsis the provision of an improved method of conducting metallic halide-catalyzed'isomerization reacf.

tions. Although the invention vis particularly ad;r vantageous in connectionwith the isomerization of normal butane, it may also be applied. to the. conversion of normal pentane and normal hexane; it is of utility in treating mixtures of these hydrocarbons, as well as in treating theml indi vidually.

The isomerizing ability possessed by certain metallic halides has engenderednurnerous Vpro-V posals for using them to convertvnorma-l parafflns into iso-parafilns. Theadvantages thus soughtV to be obtained include not only the enhancementof the octane number and direct motor fuel value of the paraflins themselves, but also the develop# ment of sufcient chemical reactivity by isomerization to permit the subsequent catalytic alkylation thereof with normally gaseous olefins, lead'- ing to the production of increased quantities of high octane fractions boiling in the motor fuel range.

As in substantially all other types of .hydrocarf bon conversions, it is preferable ina commercial.. isomerization process that the conversiontake place continuously, inorder that operating costs.

may be kept low. Continuous isomerization-YK processes heretofore known and used-have involved the passage of hydrocarbons, preferably in= the vapor phase, through a reaction Zone contain-l ing a solid or liquid body of catalytic material Y while at a suitable conversion temperature; The

chief catalystsV employed have beenbromides or r chlorides of such metals as. aluminum. andzir= conium. The latter substances are characterized by a tendency to sublime or vaporize at Itempera- A tures Within the isomerization range, andl thus'to pass out of an isomerizationreactor along with The rate at Whi'ch'hydrocarbons are convertedr byra metallic halide isomerization catalyst is pro'- foundly" influenced Vby the intimacy with which they are contacted With thev catalyst. On this account prior known methods have involved either` vigorous, agitation in the liquid phase or, intreating.A vaporized hydrocarbons, the use ofextended. surface lms of catalyst deposited upon porous.

supports. Owingto the` tendency of. the halide perplexingY problem. It is possible to avoidthegeneous yvapor phase, containing both the hydrocarbons to be converted and the catalyst. Thisg.

methodof operation provides an intimacy of contact which is'far-beyond anything attainablewith solid or liquid catalysts, ,andiaffords other advane:

tages. f

The homogeneous vapor phasemethod oficon-s. ducting catalytic isomerization necessarily inevolvestvvo moreor less-conjugated procedures,

vizi.. (1S) the vaporization and admixture ofv they hydrocarbonsand the catalyst', and (2) the vcon-A densation` and` separation Yof the thus-formed mixture into-its componentv parts, after the iso-- merization reaction has proceeded to the desiredextent- The invention'hereinafter described and claimed has for its principal-object the provision of aunitary method'ofconducting the latter two conjugated steps in Yan ecient and substantially continuous manner.

The solidisomerization catalysts used in'pra'c.- ticing the invention are, as previously pointed out, capable'of passing directly from the solid to the vapor phase, and vice versa. When a homogeneous vapor phase mixture thereof with hydrocar bon vapors is cooled to effect condensation, the

tendency. of the catalyst substances is to deposit.

as solids on the cooling surfaces and thus gradually. to reduce. the heat transfer rate thereof and4` the accessof the -vapor mixture thereto. This situation may beremedied by special arrangementsofapparatus or by periodically discontinuing operation of the condenser and removing acy Acumulated catalyst deposits. bythe present invention, however, to omit` any .v

It isI contemplated and all provisionsefor.preventing catalyst deposition'or for removingaccumulated catalyst from. coolingA surfaces.

Instead; the' deposits. are alcatalysts ,tobecome coated With heavy products. of. side-reactions, however, the-maintenance of a.- large area ofactive catalyst surface has been-a lowed to build up to a moderate extent, insuicient to interfere seriously with the functioning of the condenser, and then the flow of reactant vapors is reversed so that the accumulated catalyst deposit is stripped 01T by and admixed with fresh hydrocarbon feed vapors. By employing a pair of identical catalyst vaporizer-condenser units, situated at opposite ends of the isomerizing zone, the invention contemplates periodic ow reversal whereby each unit serves as a catalyst condenser during part of the operating time, and as a catalyst vaporizer during the remainder. Temperature conditions are so regulated that no hydrocarbons are condensed during condensation of the catalyst, that function being accomplished by a separate and subsequent condenser.

The catalysts which I use in practicing my invention are the volatile metallic halides heretofore found to possess iso-merizing activity in the solid or liquid phase. I especially prefer to use aluminum chloride, however, because its activity is high in proportion to its cost and because it is not so active as to cause excessive side reactions at the somewhat elevated temperatures required to maintain it in the vapor phase. It is now known that the metallic halides depend for their isomerization activity upon the presence of certain promoting substances, in the absence of which they are substantially inactive. The promoters thus far found to be effective have for the most part been normally gaseous halogen compounds or compounds which are productive of gaseous halogen compounds under isomerization conditions. Thus, hydrogen halides have been used to a, great extent; also, water will exercise a promoting effect on aluminum chloride because the two react to form hydrogen chloride. Other promoting substances known to be effective include certain alkyl halides, hydrogen bromide, and boron fluoride. It is contemplated by my invention to employ such a volatile promoting substance in connection with the catalysts of hydrocarbon isomerization by a vaporized metallic halide.

A general method of flow for an exemplary embodiment of my invention will now be described with reference to the accompanying diagrammatic ow sheet, wherein items of equipment are conventionally shown and from which most of the self-evident necessares such as 4 The operative rotational range of the plug is 90, and at one extreme thereof each of the four fluid connections leads via one of the plug passages to one of the two adjacent fluid connections lying on either side. At the other extreme each uid connection leads via a plug passage to the other of the two adjacent fluid connections lying on either side.

Valve ll as shown in the drawing is positioned initially so that line 3 leads through one of the plug passages into line 4. The alternate position of valve 4 is diagrammed as indicated by 4a and as will be subsequently described, provides for connecting line 3 with line 39, and line 5 with line 3|. As positioned initially, lines 30 and 3l are connected through the other plug passage of valve 4.

Continuing through line 5, the preheated hy- I drocarbon vapors enter the shell of a catalyst pumps, valves and the like have been omitted for greater clarity. It is to be understood that the particular arrangement of apparatus shown and the particular process described are illustrative only and in no way limit the scope of the invention.

In the drawing, a stream of hydrocarbon material to be subjected to isomerization is taken from any suitable source and introduced into line I for transfer to a feed vaporizer or preheater 2, which may, for example, consist esesntially of an externally heated pipe coil. If the feed is initially avaiable as a liquid it is rst vaporized in the coil 2 and then further heated, or if initially in vapor form is preheated directly Preheated hydrocarbon vapors issuing from coil 2 traverse line 3 and enter a multiport valve 4. This valve is conventionally shown and suitably consists of a plug-type Vvalve provided with four fluid connections spaced 90 apart around the body of the valve. The rotatable valve plug is bored with two independent passages, each ofV which describes a right angle so as to be capable of connecting two adjacent fluid connections.

vaporizer-condenser 6 which initially is serving as a catalyst vaporizer. Vessel 6 consists of a tube bundle 9 arranged as in a water tube-condenser, and having connections for the passage 0f water or other fluid through the tubes via inlet 'l' and outlet 8. The hydrocarbon vapors entering the-shell from line 6 contact the outside of tubes 9 and are withdrawn into line I I.

Prior to the commencement 0f the present operation, as will be hereinafter described, the outside of the tubes 9 will have been coated with a deposit of a volatile metallic halide isomerization catalyst. In passing through the shell of the vaporizer 6, the preheated hydrocarbon vapors become saturated with vaporized catayst at the existing temperature. Inasmuch as the temperature of the hydrocarbon vapors is capable of being regulated by adjustment of the heat supplied to coil 2, the proportion of metallic halide in the saturated vapors may likewise be precisely controlled.

During its service as a catalyst vaporizer, the vessel 5 need not be supplied with cooling water via connection l, and if desired steam or other heating medium may be passed through the tubes 9 to assist in vaporizing the catalyst. I prefer, however, to supply a small amount of cooling water sufficient to maintain the tube walls just below the sublimation temperature of the catalyst. In this way, it is possible to minimize the flaking'off of catalyst from the tubes and the accumulation of catalyst in the bottom end of the shell. The same object is furthered by employing tubes having artificially roughened outer surfaces. If desired the tubes 9 may be nned or baiiled in such a way as to prevent catalyst from falling to the bottom of the shell.

The mixed hydrocarbon and catalyst vapors withdrawnfrom vessel 6 into line II enter a multiport valve I2 which, as is clearly shown by the drawing, has three fluid connections spaced apart and a plug with a T-shaped passage, whereby the fluid connection to which line II is joined may lead via a right angle turn into line I3 or in a straight line (as is indicated by the diagram I2a) into line 49. In the initial operation the valve is positioned so as to divert the mixture of hydrocarbon and catalyst vapors into line I3, whence they pass to another multiport valve I4, the mode of operation of which will be clear from the already given descriptions of valves 4 and I 2. Via valve I4 the reactant mixture passes into line I5 and is joined by a gaseous stream of a suitable promoter substance, such as dry hydrogen chloride gas, introduced through line i6. The complete mixture next enters a heat exassesses changer `vll iwherein it 'is i heated toi-ther desiredLY reaction temperature. It-continuesthrough line I8 into `an empty reactor vessel -I 9 the -interiorofwhichconstitutes the -isorneriZation-v reaction zone, The -vessel I9 is made of such a volumetric capacity asfwill provide `a sufficient time of! transit of the reactant gas Y mixture therethrough;4 during-which the isomerization of the hydrocarbons proceeds to the desired extent. Upon issuing from the reaction zone the reactant gas fmix` ture travels through line 2| to a multiport valve 2 which,` as is indicated inthe drawing,serves`to divert the stream into line 23 in this initial op# eration. An alternate position of valve 22 yi* shown in the adjacent diagram 22a.'

From line 23 the reactant gas mixture trav-l erses multiport valve 24 into nline 25 and thence# enters a second catalyst vaporizer-condenser 25,`4 which in this initial operation is serving as a catalyst condenser. The'construction of 26 is identical in all respects with that of vessel 6 'already described, and comprises tubes 29 which are sup plied with water via inlet 21 and outlet 28.

As the reactant gas mixture enters the shell of the catalyst condenser 25, water is being passed" through the tubes at a temperature and rate` sufcient to cool the mixture to a point just slightly above'the dew point of the hydrocarbons therein. At such a temperature substantially all or at least a major portion of the catalyst con-V denses as a solid on the exterior of the tubes 29, while the hydrocarbons and promoter substance vremain uncondensed. The latter materials, together with minor amounts of the catalytic metallic halide vapors, are withdrawn from the shell of condenser 29 into line 30, and after traversing multiport valve 4 as indicated, `they pass through line 3l into a product condenser 32. Water is passed through the shell of the tubular condenser 32 via inlet 33 and outlet 34; the` entering gas mixture is introduced into the tubes, wherein by indirect heat exchange the temperature is lowered and all constituents are condensed except the normally gaseous promoter substance. The latter material should, in practicing this em` bodiment oi the invention, have a substantially higher volatility than either the hydrocarbons or the metallic halide catalyst.

In condenser 32 the ow of the condensing vapors' is upwardly through the externally cooled tubes '29 which are preferably of relatively/large diameter. Hydrocarbons which condense in theupper portions of the tubes ow downwardly along the inside walls thereof, so that the minor amounts of metallic halide catalyst also condensed are prevented from depositing directly on the tube Walls and obstructing the passing of the rising vapors. A suspension of solidified metallic halide in liquid hydrocarbon material is carried down into the bottom of condenser and drawn off to line 35. Gaseous promoter material re-l mains uncondensed, and is removed from the upper end of condenser 29 into line I6 for re-admixture withv additional quantities of reactants,

as previously described.

The liquefied hydrocarbons withdrawn into line are passed to a settling drum 36 wherein thesmall amounts of solidied metallic halide catalyst are separated by gravity. They are removed as a slurry by drawing them ofi from the bottom of the settler 33 into line 31, whence they may be transferred to a recovery step suitably involving vaporization of the accompanying hy-` drocarbon material by heating or pressure reduction.A Any suitable method maybe used `for' `vThe vreactantmaterials-y leaving. reactor 6? recoveringthe V`traces offcatalystlfcarriedibverf soJ thatit may be re-used in the process."-

Y"Ih'e'1clear supernatant "hydrocarbon lliduidis' i Withdrawn ffr'omsettl'er' 3 6 Athrough -line 38;:v and `a it-con'stitute's the grossconversion'productfof the process it -maybrdisposed ofasl-desired:v Irl-ther caseof- :butaneY-isomerization' it will' ordinarily r'be' preferabletofseparate thaise-butano made--`in1theprocess from iunconvert'ed normal vbutane. the-f lflatter being then recycled for furth'erfconversion* along-Withlfadditional amounts'of lfresh-feed? As will be hereinafter more specifically explained, al high- -percentconver'sion lofnormal -tc' -'iso -icomle pounds in blissl thiugh" the reaction! zone is" T29 in the catalyst condenser'26wil1lbecome ccatv ed -with catalyst to suclilan extent that their-icapacityzfor heat removal `will lbefredu'ced.-lv .Lit-an`lvl^ appropriate ipointg-before eitlierofS the -latteritvvo -v occurrences fhave proceeded'farlenough tofinteri f reduced whilean'ff abundant supply oit-cooling.wa-L-` ter is supplied to vaporizerl; Thereupon vapor;

izer f6 "becomesioperative as a catalystcondensen' andfcondens'er 26 Abecomes operative ias acatalyst'V il uivaporizerf, The newly established vflow -of hydro--Y carbons; catalyst and promoter substance iszthenl as-follow's: From line Btl-1e preheatdfvaporspass 1i into vline 30; thence through the vaporizer :I 2-6 wherein they iare "saturated with catalyst; thence through'line v2 5,'valve :24,1ine139 zand valve i I4 inV to Wline-'2| 5 wherein Tthey V.are fadmixed with pro# moter :substance-"and thence throughfline "I 8 4fandr heatlexchanger 1H `into'reactor I 9 Ias "alreadyssdee' scribed' with 4reference "to 'the initial operatione- I9 f through line 2| go through Valve-22 into :line:49;f, thence through valvefl 2 into line! I,;and the icatM-v alyst is condensedV out in` f6; 'i Hydrocarbons `land; promoter material leave the condenserrthrough `line l5 and after traversingf-valvellinto'line/Bil they enter product lcondenser '20; after which-1 they v-are handled in exactly 'the Ysame fmanner :as fr has already been described with reference to-the-1 initial operation.A

It will be understood lby hydrocarbon'- processi engineers 'that numerous proceduralV steps* inY the@l above described embodiment 'of my invention mayl.-4 be Y*replaced by; alternate 'andr equivalent steps-f- For example; I may: accomplish the vap'orizationk of a metallic'halide fcatalyst bypassingeonlyxaf portion?` of the vaporized hydrocarbon vvcharge through a catalyst vaporizen vreunitingfthis 'cat--V alyst vapor-carringzporti'on with the :main charge' streamprior to its entry 'into' thev reaction* zone:` With thelatterv arrangement it lis' possible 'todise4 pense withlthe exchanger :I vl, and t0C vaporizei-and heat 'J the. charge' directly-to an isomer-izing temperature''linithe"feed-'vaporizer 2: The:amount of catalyst vapor: admixetr` with: the chargel is then controlled by varying the proportion of thev pressure high enough to dissolve a lsubstantial 1 amount of the promoting substance in the re-l action products condensing in 32, and to separate the promoter for re-use in a subsequent fractional distillation of the hydrocarbon liquid Withdrawn through line 38.

The operations thus far described have assumed the initial presence of a coating of catalyst on the exterior of the tubes 9 in condenser-vaporizer 6. Such a deposit may be formed prior to the commencement of hydrocarbon conversion by passing heated air through a body of catalyst in any suitable container and then leading the catalyst-saturated air through the vessel the tubes of which are to be coated, while passing cooling water through said tubes to condense out catalyst thereon. This operation is necessarily repeated during -occasional shut-downs of the conversion operation, in order to return to the system those small amounts of catalyst which escape through line 31.

Referring now more specifically to the operating conditions which are usuable and desirable in practicing the invention, it will be understood that the temperature of hydrocarbon vapors passed through a catalyst vaporizer such as 6 in the drawing is readily chosen in accordance with known principles of vaporization so that the hydrocarbon vapors will, when saturated therewith, contain a proper amount of the catalyst vapors. The requisite temperature at which to vaporize the catalyst is jointly determined by the per cent catalyst vapors desired in the reactant mixture, the temperature-vapor pressure characteristics of the chosen metallic halide catalyst, and the pressure. The rst of the latter three variables is subject to considerable variation, depending upon the activity of the particular catalyst employed, the type of hydrocarbons to be treated, and the extent of conversion desired. It may range from as low as 1 mol per cent up to about l mol per cent of the weight of the hydrocarbon charge. The pressure in the catalyst vaporizer is preferably the same as that desired to be maintained in the conversion zone, of which more will be said. There must of courserbe a sufficient quantity of catalyst in the vaporizer vessel to enable a state of saturation to be attained by the hydrocarbon vapors while they are in contact therewith. y Y

Referring now to the conditions in the conversion zone itself, it will be understood that the pressure and temperature are necessarily limited to those conditions which will maintain the hydrocarbon charge in the Vapor phase. I prefer, furthermore, that in no case shall the temperature be lower than about 200 F. nor higher than about 700 F., for at lower temperatures only minute amounts of catalyst can exist as vapor in admixture with the hydrocarbons, and at higher temperatures side reactions supervene.

The conversion pressure, except as it is limited by the foregoing considerations, may be'from atmospheric to about 2000 pounds per square inch. The higher rpressures must in geneial be accompanied by higher temperatures in order to maintain both the charge and the catalyst in vapor phase. The choice of a temperaturel and pressure at which to carry out the isomerization reaction is, as previously indicated-limitedby 8 the per cent catalyst vapors desired to be present, and vice versa, inasmuch as the per cent of catalyst vapor which can be maintained in a hydrocarbon vapor saturated therewith varies inversely With the system pressure and directly with the temperature. Thus, if aluminum chloride is taken as the catalyst and a concentration of 10 mol per cent thereof is to be maintained in the reaction zone, the temperature must be not lower than about 300 F. at'atmospheric pressure, and not lower than about 350 F. at 100 pounds per square inch absolute, for otherwise the desired catalyst concentration will be above the saturation point of the hydrocarbon charge.

The reaction times and the promoter concentrations which are usable in practicing the invention are likewise amenable to considerable variation. The reaction time can be as short as one minute or as long as several hours, depending uporrthe type of hydrocarbon material treated and the extent of conversion desired. The longer reaction times are not very practicable in a commercial operation, however, because of the unduly large reaction vessel which they require. The latter diiliculty is made somewhat less acute by operating at the higher pressures. The promoter concentration in the reactant vapor mixture is preferably between about 1 and about 10 mol per cent of the hydrocarbon, about 5 per cent being preferred.

An important limitation exists as to the pressure and temperature conditions which may be permitted to exist in a catalyst condenser such as 26 in the initial operation previously described. As already mentioned, the temperature in such a condenser must be kept above the dew point of the hydrocarbon vapors, in order to prevent condensation thereof. It must also be low enough to accomplish the condensation of a major portion and preferably substantially all of the catalyst. Both the latter requirements are influenced by the pressure, and the former is influenced by the volatility of the hydrocarbons treated. In order that there may be a temperature capable of satisfying both the latter requirements, the pressure must be limited. Thus in the case of butane isomerization the pressure during catalyst condensation should be below 500 pounds and is preferably below 300 pounds, while for pentane, A

the corresponding pressures are 200 and pounds respectively, assuming the use of aluminum chloride as a catalyst. A suitable pressure is readily calculable in any given case using published thermodynamic data. In the event that the requisite catalyst condensation pressure is below the desired conversion pressure, expansion of the reacted vapor mixture prior to catalyst condensation will be necessary.

While I have described my invention with reference to certain embodiments thereof for illustrative purposes, my invention is limited only by the following claims.

I claim:

1. The method for isomerizing hydrocarbons which comprises passing hot hydrocarbon vapors through a catalyst vaporizing and condensing zone and into contactA therein with a normally solid volatile metallic halide isomerizing catalyst deposited in solid form upon the heat transferring'surfaces of means adapted for the indirect exchange of heat betweendilferent fluid streams to effect the formation of a vaporous mixture of hydrocarbon vapors and vapors of the normally solid metallic halide isomerizing catalyst, passing the resulting vaporous mixture out of contact with said solid metallic halide catalyst and into an isomerization reaction zone free from deposited solid metallic halide isomerzing catalyst and suciently large to provide a holding time eiective to permit the reaction to proceed, maintaining said gaseous mixture in said reaction zone under isomerizing conditions which prevent any substantial condensation of said vaporized metallic halide catalyst in said reaction rsone, then passing said reaction mixture through a second catalyst vaporizing and condensing Zone in contact with heat transferring surfaces of means adapted for the indirect exchange of heat between different streams, maintaining said heat transferring surfaces in said second catalyst vaporizing and condensing zone sufficiently cool to effect substantial condensation and deposition of said normally solid metallic halide isomerizing catalyst without condensing hydrocarbons, then reversing the flow of the vaporized hydrocarbons whereby they flow first through said second catalyst vaporizing and condensing zone to vaporize metallic halide isomerizing catalyst previously condensed and deposited therein from the said vaporous mixture of hydrocarbon and metallic halide vapors, passing the last-mentioned vaporous mixture through the reaction zone in the manner described, and then passing the reaction mixture from the reaction Zone through said iirst catalyst vaporizing and condensing zone under conditions effective to condense and deposit therein metallic halide isomerizing catalyst without condensing hydrocarbons.

2. A process in accordance with claim 1 wherein normal parai'n hydrocarbons of 4 to 6 carbon atoms to the molecule are isomerized.

3. The method for isomerizing hydrocarbons which comprises passing hot hydrocarbon vapors through a catalyst vaporizing and condensing zone and into contact therein with an aluminum chloride isomerizing catalyst deposited in solid form upon the heat transferring surfaces of means adapted for the indirect exchange of heat between diiferent fluid streams to effect the formation of a vaporous mixture of hydrocarbon vapors'and vapors of the aluminum chloride isomerizing catalyst, passing the resulting vaporous mixture out of contact with said solid aluminum chloride and into an isomerization reaction Zone free from deposited solid aluminum chloride and suciently large to provide a holding time effective to permit the reaction to proceed, maintaining said gaseous mixture in said reaction Zone under isomerizing conditions which prevent any substantial condensation of said vaporized aluminum chloride in said reaction zone, then passing said reaction mixture through a second catalyst vaporizing and condensing zone in contact with heat transferring surfaces of means adapted for the indirect exchange of heat between different streams, maintaining said heat transferring surfaces in said second catalyst Vaporizing and condensing Zone sufficiently cool to effect substantial condensation and deposition of said aluminum chloride isomerizing catalyst without condensing hydrocarbons, then reversing the flow of the vaporized hydrocarbons whereby they new first through said second catalyst vaporizing and condensing zone to vaporize aluminum chloride isomerizing catalyst previously condensed and deposited therein from the said vaporous mixture l@ of hydrocarbon and aluminum chloride vapors, passing the last-mentioned vaporous mixture through the reaction Zone in the manner described, and then passing the reaction mixture from the reaction zone through said first catalyst vaporizing and condensing Zone under conditions effective to condense and deposit therein aluminum chloride isomerizing catalyst without condensing hydrocarbons.

4. The method for isomerizing hydrocarbons which comprises passing hot hydrocarbon vapors through a catalyst vaporizing and condensing zone and into contact therein with a normally solid volatile metallic halide isomerizing catalyst deposited in solid form upon the heat transferring surfaces of means adapted for the indirect Y exchange of heat between different fluid streams to effect the formation of a vaporous mixture of hydrocarbon vapors and vapors of the normally solid metallic halide isomerizing catalyst, passing the resulting vaporous mixture out of contact with said solid metallic halide catalyst and into an isomerization reaction zone of relatively large cross-sectional area and free from deposited solid metallic halide isomerizing catalyst and sufficiently large to provide a holding time effective to permit the reaction to proceed, maintaining said gaseous mixture in said reaction Zone under isomerizing conditions which prevent ani7 substantal condensation of said vaporized metallic halide catalyst in said reaction Zone, then passing said reaction mixture through a second catalyst Vaporizing and condensing zone in contact with heat transferring surfaces of means adapted for the indirect exchange of heat between different streams, maintaining said heat transferring surfaces in said second catalyst vaporizing and condensing zone suficiently cool to eifect substantial condensation and deposition of said normally solid metallic halide isomeriZing catalyst without condensing hydrocarbons, then reversing the flow of the vaporized hydrocarbons whereby they iiow rst through said second catalyst vaporizing and condensing zone to vaporize metallic halide isomerizing catalyst previously condensed and deposited therein from the said vaporous mixture of hydrocarbon and metallic halide vapors, passing the last-mentioned vaporous mixture through the reaction Zone in the manner described, and then passing the reaction mixture from the reaction zone through said rst catalyst vaporizing and condensing zone under conditions effective to condense and deposit therein metallic halide isomerizing catalyst without condensing hydrocarbons.

ERNEST SOLOMON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,277,022 McMillan et al Mar. 17, 1942 2,281,924 De Simo et al. May 5, 1942 2,324,746 Weinrich et al July 20, 1943 2,343,406 Dryer Mar. 7, 1944 FOREIGN PATENTS Number Country Date 377,663 Italy Jan. 2, 1940 

